NetMQ PUSH socket blocks indefinitely when it reaches HWM - zeromq

I'm using NetMQ (Nuget 3.3.2.2) on .NET 4.5 and I have a single fast generator process with a PUSH socket, and a single slow consumer process using a PULL socket. If I send enough messages to hit the sending HWM, the sending process blocks the thread indefinitely.
Some contrived (generator) code which illustrates the problem:
using (var ctx = NetMQContext.Create())
using (var pushSocket = ctx.CreatePushSocket())
{
pushSocket.Connect("tcp://127.0.0.1:42404");
var template = GenerateMessageBody(i);
for (int i = 1; i <= 100000; i++)
{
pushSocket.SendMoreFrame("SampleMessage").SendFrame(Messages.SerializeToByteArray(template));
if (i % 1000 == 0)
Console.WriteLine("Sent " + i + " messages");
}
Console.WriteLine("All finished");
Console.ReadKey();
}
On my configuration, this will usually report it has sent about 5000 or 6000 messages, and will then simply block. If I set the send HWM set to a large value (or 0), then it sends all of the messages as expected.
It looks like it's waiting to receive another command before it tries again, here: (SocketBase.TrySend)
// Oops, we couldn't send the message. Wait for the next
// command, process it and try to send the message again.
// If timeout is reached in the meantime, return EAGAIN.
while (true)
{
ProcessCommands(timeoutMillis, false);
From what I've read in the 0MQ guide, blocking on a full PUSH sockeet is the correct behaviour (and is what I want it to do), however I would expect it to recover once the consumer has cleared its queue.
Short of using some sort of TrySend pattern and dealing with the block myself, is there some option I can set or some other facility I can use to have the PUSH socket attempt to resend blocked messages periodically?

Related

Is There way to find the queue is empty using rabbit-template

I have subscriber which collects the messages until reaches the specified limit and then pass collected messages to the processor to perform some operations. Code works fine, problem is subscriber waits Until it collects specified number messages. If we have lesser message program control will not pass to processor.
For example Lets say my chunk size is 100 and if I have 100 or multiple of 100 messages then program works fine But if I have messages < 100 or 150 some of messages are read by subscriber but they were never passed to processor. Is there way I can figure-out is that Queue is empty using rabbit template so that I can check that condition and break the loop
#RabbitListener(id="messageListener",queues = "#{rabbitMqConfig.getSubscriberQueueName()}",containerFactory="queueListenerContainer")
public void receiveMessage(Message message, Channel channel, #Header("id") String messageId,
#Header("amqp_deliveryTag") Long deliveryTag) {
LOGGER.info(" Message:"+ message.toString());
if(messageList.size() < appConfig.getSubscriberChunkSize() ) {
messageList.add(message);
deliveryTagList.add(deliveryTag);
if(messageList.size() == appConfig.getSubscriberChunkSize()) {
LOGGER.info("------------- Calling Message processor --------------");
Message [] messageArry = new Message[messageList.size()];
messageArry = messageList.toArray(messageArry);
LOGGER.info("message Array Length: "+messageArry.length);
messageProcessor.process(messageArry);
messageList = new ArrayList<Message>(Arrays.asList(messageArry));
LOGGER.info("message Array to List conversion Size: "+messageList.size());
LOGGER.info("-------------- Completed Message processor -----------");
eppQ2Publisher.sendMessages(messageList, channel, deliveryTagList);
messageList.clear();
deliveryTagList.clear();
}
} else {
// do nothing..
}
There are two ways to achieve this.
Add an #EventListener to listen for ListenerContainerIdleEvents which are published when no messages have been received for some time; set the container's idleEventInterval property. The source of the event is the listener container; it contains the #RabbitListener's id. See Detecting Idle Consumers.
Use RabbitAdmin.getQueueProperties().
You can use RabbitAdmin.getQueueInfo("queue name").getMessageCount() that will be 0 for empty queue.

Can't pass OVERLAPPED object to WSAGetOverlappedResult

I'm trying to develop req/res server by using overlapped io according to this example.
The problem is that in the same time there could be multiple sends to the same socket and I can't pass overlapped structure to the WSAGetOverlappedResult to manage send event properly. The main loop looks like:
while (TRUE) {
index = WSAWaitForMultipleEvents(EventTotal, EventArray, FALSE, WSA_INFINITE, TRUE);
if (index == WSA_WAIT_FAILED) {
printf("Wait failed w/err %d\n", WSAGetLastError());
continue;
}
index -= WSA_WAIT_EVENT_0;
if (!WSAEnumNetworkEvents(SocketArray[index]->Socket, EventArray[index], &NetworkEvents)) { // Multiple events max exist
if (NetworkEvents.lNetworkEvents & FD_ACCEPT)
ManageAccept(index, NetworkEvents);
if (NetworkEvents.lNetworkEvents & FD_READ)
ManageRead(index, NetworkEvents);
if (NetworkEvents.lNetworkEvents & FD_WRITE)
ManageWrite(index, NetworkEvents);
}
}
Then I send messages from method ManageRead to the client socket with
WSASend(SocketArray[index]->Socket, &(over->wsabuf), 1, &SendBytes, 0, over, NULL)
And when overlapped send completed I can't really realize in the method ManageSend which of the overlapped structures was actually sent with the call WSAGetOverlappedResult:
WSAGetOverlappedResult(SocketArray[index]->Socket, over, &SendBytes, FALSE, &flags)
I have to use WorkerRoutine temporary to gain control over sending but perhaps somebody knows how to address the issue. Or may there is some different method which returns the overlapped structure which was completed?

routing files with zeromq (jeromq)

I'm trying to implement a "file dispatcher" on zmq (actually jeromq, I'd rather avoid jni).
What I need is to load balance incoming files to processors:
each file is handled only by one processor
files are potentially large so I need to manage the file transfer
Ideally I would like something like https://github.com/zeromq/filemq but
with a push/pull behaviour rather than publish/subscribe
being able to handle the received file rather than writing it to disk
My idea is to use a mix of taskvent/tasksink and asyncsrv samples.
Client side:
one PULL socket to be notified of a file to be processed
one DEALER socket to handle the (async) file transfer chunk by chunk
Server side:
one PUSH socket to dispatch incoming file (names)
one ROUTER socket to handle file requests
a few DEALER workers managing the file transfers for clients and connected to the router via an inproc proxy
My first question is: does this seem like the right way to go? Anything simpler maybe?
My second question is: my current implem gets stuck on sending out the actual file data.
clients are notified by the server, and issue a request.
the server worker gets the request, and writes the response back to the inproc queue but the response never seems to go out of the server (can't see it in wireshark) and the client is stuck on the poller.poll awaiting the response.
It's not a matter of sockets being full and dropping data, I'm starting with very small files sent in one go.
Any insight?
Thanks!
==================
Following raffian's advice I simplified my code, removing the push/pull extra socket (it does make sense now that you say it)
I'm left with the "non working" socket!
Here's my current code. It has many flaws that are out of scope for now (client ID, next chunk etc..)
For now, I'm just trying to have both guys talking to each other roughly in that sequence
Server
object FileDispatcher extends App
{
val context = ZMQ.context(1)
// server is the frontend that pushes filenames to clients and receives requests
val server = context.socket(ZMQ.ROUTER)
server.bind("tcp://*:5565")
// backend handles clients requests
val backend = context.socket(ZMQ.DEALER)
backend.bind("inproc://backend")
// files to dispatch given in arguments
args.toList.foreach { filepath =>
println(s"publish $filepath")
server.send("newfile".getBytes(), ZMQ.SNDMORE)
server.send(filepath.getBytes(), 0)
}
// multithreaded server: router hands out requests to DEALER workers via a inproc queue
val NB_WORKERS = 1
val workers = List.fill(NB_WORKERS)(new Thread(new ServerWorker(context)))
workers foreach (_.start)
ZMQ.proxy(server, backend, null)
}
class ServerWorker(ctx: ZMQ.Context) extends Runnable
{
override def run()
{
val worker = ctx.socket(ZMQ.DEALER)
worker.connect("inproc://backend")
while (true)
{
val zmsg = ZMsg.recvMsg(worker)
zmsg.pop // drop inner queue envelope (?)
val cmd = zmsg.pop //cmd is used to continue/stop
cmd.toString match {
case "get" =>
val file = zmsg.pop.toString
println(s"clientReq: cmd: $cmd , file:$file")
//1- brute force: ignore cmd and send full file in one go!
worker.send("eof".getBytes, ZMQ.SNDMORE) //header indicates this is the last chunk
val bytes = io.Source.fromFile(file).mkString("").getBytes //dirty read, for testing only!
worker.send(bytes, 0)
println(s"${bytes.size} bytes sent for $file: "+new String(bytes))
case x => println("cmd "+x+" not implemented!")
}
}
}
}
client
object FileHandler extends App
{
val context = ZMQ.context(1)
// client is notified of new files then fetches file from server
val client = context.socket(ZMQ.DEALER)
client.connect("tcp://*:5565")
val poller = new ZMQ.Poller(1) //"poll" responses
poller.register(client, ZMQ.Poller.POLLIN)
while (true)
{
poller.poll
val zmsg = ZMsg.recvMsg(client)
val cmd = zmsg.pop
val data = zmsg.pop
// header is the command/action
cmd.toString match {
case "newfile" => startDownload(data.toString)// message content is the filename to fetch
case "chunk" => gotChunk(data.toString, zmsg.pop.getData) //filename, chunk
case "eof" => endDownload(data.toString, zmsg.pop.getData) //filename, last chunk
}
}
def startDownload(filename: String)
{
println("got notification: start download for "+filename)
client.send("get".getBytes, ZMQ.SNDMORE) //command header
client.send(filename.getBytes, 0)
}
def gotChunk(filename: String, bytes: Array[Byte])
{
println("got chunk for "+filename+": "+new String(bytes)) //callback the user here
client.send("next".getBytes, ZMQ.SNDMORE)
client.send(filename.getBytes, 0)
}
def endDownload(filename: String, bytes: Array[Byte])
{
println("got eof for "+filename+": "+new String(bytes)) //callback the user here
}
}
On the client, you don't need PULL with DEALER.
DEALER is PUSH and PULL combined, so use DEALER only, your code will be simpler.
Same goes for the server, unless you're doing something special, you don't need PUSH with ROUTER, router is bidirectional.
the server worker gets the request, and writes the response back to
the inproc queue but the response never seems to go out of the server
(can't see it in wireshark) and the client is stuck on the poller.poll
awaiting the response.
Code Problems
In the server, you're dispatching files with args.toList.foreach before starting the proxy, this is probably why nothing is leaving the server. Start the proxy first, then use it; Also, once you call ZMQProxy(..), the code blocks indefinitely, so you'll need a separate thread to send the filepaths.
The client may have an issue with the poller. The typical pattern for polling is:
ZMQ.Poller items = new ZMQ.Poller (1);
items.register(receiver, ZMQ.Poller.POLLIN);
while (true) {
items.poll(TIMEOUT);
if (items.pollin(0)) {
message = receiver.recv(0);
In the above code, 1) poll until timeout, 2) then check for messages, and if available, 3) get with receiver.recv(0). But in your code, you poll then drop into recv() without checking. You need to check if the poller has messages for that polled socket before calling recv(), otherwise, the receiver will hang if there's no messages.

How to continuously read JMS Messages in a thread and achnowledge them based on their JMSMessageID in another thread?

I've written a Continuous JMS Message reveiver :
Here, I'm using CLIENT_ACKNOWLEDGE because I don't want this thread to acknowledge the messages.
(...)
connection.start();
session = connection.createQueueSession(true, Session.CLIENT_ACKNOWLEDGE);
queue = session.createQueue(QueueId);
receiver = session.createReceiver(queue);
While (true) {
message = receiver.receive(1000);
if ( message != null ) {
// NB : I can only pass Strings to the other thread
sendMessageToOtherThread( message.getText() , message.getJMSMessageID() );
}
// TODO Implement criteria to exit the loop here
}
In another thread, I'll do something as follows (after successful processing) :
This is in a distinct JMS Connection executed simultaneously.
public void AcknowledgeMessage(String messageId) {
if (this.first) {
this.connection.start();
this.session = this.connection.createQueueSession( false, Session.AUTO_ACKNOWLEDGE );
this.queue = this.session.createQueue(this.QueueId);
}
QueueReceiver receiver = this.session.createReceiver(this.queue, "JMSMessageID='" + messageId + "'");
Message AckMessage = receiver.receive(2000);
receiver.close();
}
It appears that the message is not found (AckMessage is null after timeout) whereas it does exist in the Queue.
I suspect the message to be blocked by the continuous input thread.. indeed, when firing the AcknowledgeMessage() alone, it works fine.
Is there a cleaner way to retrieve 1 message ? based on its QueueId and messageId
Also, I feel like there could be a risk of memory leak in the continuous reader if it has to memorize the Messages or IDs during a long time.. justified ?
If I'm using a QueueBrowser to avoid impacting the Acknowledge Thread, it looks like I cannot have this continuous input feed.. right ?
More context : I'm using ActiveMQ and the 2 threads are 2 custom "Steps" of a Pentaho Kettle transformation.
NB : Code samples are simplified to focus on the issue.
Well, you can't read that message twice, since you have already read it in the first thread.
ActiveMQ will not delete the message as you have not acknowledge it, but it won't be visible until you drop the JMS connection (I'm not sure if there is a long timeout here as well in ActiveMQ).
So you will have to use the original message and do: message.acknowledge();.
Note, however, that sessions are not thread safe, so be careful if you do this in two different threads.

Issue or confusion with JMS/spring/AMQ not processing messages asynchronously

We have a situation where we set up a component to run batch jobs using spring batch remotely. We send a JMS message with the job xml path, name, parameters, etc. and we wait on the calling batch client for a response from the server.
The server reads the queue and calls the appropriate method to run the job and return the result, which our messaging framework does by:
this.jmsTemplate.send(queueName, messageCreator);
this.LOGGER.debug("Message sent to '" + queueName + "'");
try {
final Destination replyTo = messageCreator.getReplyTo();
final String correlationId = messageCreator.getMessageId();
this.LOGGER.debug("Waiting for the response '" + correlationId + "' back on '" + replyTo + "' ...");
final BytesMessage message = (BytesMessage) this.jmsTemplate.receiveSelected(replyTo, "JMSCorrelationID='"
+ correlationId + "'");
this.LOGGER.debug("Response received");
Ideally, we want to be able to call out runJobSync method twice, and have two jobs simultaneously operate. We have a unit test that does something similar, without jobs. I realize this code isn't very great, but, here it is:
final List result = Collections.synchronizedList(new ArrayList());
Thread thread1 = new Thread(new Runnable(){
#Override
public void run() {
client.pingWithDelaySync(1000);
result.add(Thread.currentThread().getName());
}
}, "thread1");
Thread thread2 = new Thread(new Runnable(){
#Override
public void run() {
client.pingWithDelaySync(500);
result.add(Thread.currentThread().getName());
}
}, "thread2");
thread1.start();
Thread.sleep(250);
thread2.start();
thread1.join();
thread2.join();
Assert.assertEquals("both thread finished", 2, result.size());
Assert.assertEquals("thread2 finished first", "thread2", result.get(0));
Assert.assertEquals("thread1 finished second", "thread1", result.get(1));
When we run that test, thread 2 completes first since it just has a 500 millisencond wait, while thread 1 does a 1 second wait:
Thread.sleep(delayInMs);
return result;
That works great.
When we run two remote jobs in the wild, one which takes about 50 seconds to complete and one which is designed to fail immediately and return, this does not happen.
Start the 50 second job, then immediately start the instant fail job. The client prints that we sent a message requesting that the job run, the server prints that it received the 50 second request, but waits until that 50 second job is completed before handling the second message at all, even though we use the ThreadPoolExecutor.
We are running transactional with Auto acknowledge.
Doing some remote debugging, the Consumer from AbstractPollingMessageListenerContainer shows no unhandled messages (so consumer.receive() obviously just returns null over and over). The webgui for the amq broker shows 2 enqueues, 1 deque, 1 dispatched, and 1 in the dispatched queue. This suggests to me that something is preventing AMQ from letting the consumer "have" the second message. (prefetch is 1000 btw)
This shows as the only consumer for the particular queue.
Myself and a few other developers have poked around for the last few days and are pretty much getting nowhere. Any suggestions on either, what we have misconfigured if this is expected behavior, or, what would be broken here.
Does the method that is being remotely called matter at all? Currently the job handler method uses an executor to run the job in a different thread and does a future.get() (the extra thread is for reasons related to logging).
Any help is greatly appreciated
not sure I follow completely, but off the top, you should try the following...
set the concurrentConsumers/maxConcurrentConsumers greater than the default (1) on the MessageListenerContainer
set the prefetch to 0 to better promote balancing messages between consumers, etc.

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